This is a comprehensively revised application of the Assessment Core of the original submission under a new name which better reflects the mission of this Core. The Interdisciplinary Research Methods Core (IRMC) will support the Center's central research agenda which is focused on understanding sexuality and gender in the context of HIV risk, and on developing interventions designed to reduce the spread of HIV and to improve long-term survival and quality of life of persons with HIV/AIDS. The previous Psychosexual Core and Psychosocial/Qualitative Assessment Core developed expertise in the conceptualization and assessment of sexual risk behavior, gender scripts, and other aspects of sexuality; the investigation of psychological adaptation and of health behavior and attitude; and the formulation of risk-preventive interventions, employing both quantitative and, increasingly, qualitative approaches. We now propose an Interdisciplinary Research Methods Core that integrates the expertise of these two antecedent Cores. The IRMC has three specific aims: (1) Project consultation: To serve as the central advisory resource for HIV Center investigators on the characterization of study populations (especially determinants and contexts of people's sexual lives); conceptualization of explanatory models; conceptualization and operationalization of outcomes, mediating factors, and intervention process factors; and development and implementation of interventions; (2) Training and education: To serve as a resource for Centerwide training in HIV-related sex research and prevention science including ethnographic, qualitative and quantitative approaches and instruments; and (3) Science development: To serve as a venue for synthesizing discussion of emerging theoretical and methodological challenges in HIV-related sexual behavior and sexual risk intervention science, including investigators from the HIV Center and other institutions. The IRMC centralizes the expertise of an interdisciplinary group of specialists in diverse areas of HIV-related behavioral research and can, thereby, provide efficient consultations to investigators from project conception through the final phase of data interpretation and reporting. Investigators' access to the Core will alleviate major logistical and financial burdens of project implementation. In addition, Core members will participate in Center-wide training/education activities and in the dissemination of theoretical and methodological approaches beyond the HIV Center. The Core will also provide a forum for exchange among investigators from a variety of behavioral-science disciplines in the exploration of cutting-edge issues in HIV prevention science.